Why carrier coverage maps can be wrong
Coverage maps are predictions of outdoor signal — useful, but not the same as what your phone gets indoors.
Last updated .
Short answer
Carrier and FCC mobile coverage maps are computer-modeled estimates of outdoor signal, not measurements of what you’ll get inside your home. Real-world results vary with terrain, buildings, foliage, your specific phone, and congestion, so maps tend to look more optimistic than reality. The only reliable test is trying the network where you actually spend time.
What “modeled coverage” means
Carriers estimate coverage by modeling signal propagation from their towers, then publish the result as a map. It’s a prediction, not a survey of your living room. The modeled nature is why two people standing in the same “covered” spot can have very different experiences.
Why your reality differs
- Buildings. Walls, metal, and low-E glass cut signal — especially higher-frequency 5G.
- Terrain & foliage. Hills and trees block or weaken signal.
- Bands. A map may count low-band coverage that’s weak indoors as “covered.”
- Your device. Older phones support fewer bands and have weaker antennas.
- Congestion. A busy tower slows everyone, and may deprioritize MVNO traffic.
How to get the truth
- Compare each carrier’s map for your home, work, and commute — note mid-band vs low-band 5G.
- Cross-check independent, crowdsourced coverage maps for a reality check.
- Test the network yourself with a trial or cheap prepaid/MVNO SIM before switching.
- If indoor signal is the problem, look at Wi-Fi calling or a signal booster.
Frequently asked questions
Why does my phone have no signal where the map shows coverage?
Coverage maps predict outdoor signal using models, not measurements inside buildings. Walls, terrain, foliage, your specific phone, and network congestion can all reduce real-world signal below what the map suggests.
How can I really tell if a carrier works where I live?
Test it. Use a free trial, an eSIM trial, or a cheap prepaid/MVNO SIM on that network for a week at home, work, and along your commute. Real-world testing beats any map.
Sources, dates & limitations
-
Data as of September 10, 2026. Last checked September 13, 2026.
-
Data as of September 10, 2026. Last checked September 13, 2026.
-
Data as of July 17, 2020. Last checked September 13, 2026.
-
Establishing the Digital Opportunity Data Collection, Third Report and Order (FCC 21-20, WC Docket No. 19-195) — Federal Communications Commission (opens in a new tab) Official (government)
Data as of January 19, 2021. Last checked September 13, 2026.
-
2024 Communications Marketplace Report (FCC 24-136, GN Docket No. 24-119) — Federal Communications Commission (opens in a new tab) Official (government)
Data as of December 31, 2024. Last checked September 13, 2026.
-
Find Home Internet and Cell Phone Coverage In Your Area (coverage map and its disclaimer) — Verizon (opens in a new tab) Provider-owned
Data as of September 13, 2026. Last checked September 13, 2026.
-
About Network Management — Verizon (opens in a new tab) Provider-owned
Data as of September 13, 2026. Last checked September 13, 2026.
-
Data as of August 23, 2023. Last checked September 13, 2026.
Limitations & caveats
- The federal rules say what carriers must model, not what any single map shows on a given day. 47 CFR 1.7004(c)(5) requires submitted propagation maps to “depict outdoor coverage,” and the FCC explained in FCC 21-20 that “[s]ignal strength maps should reflect outdoor coverage only.” Nothing in the rules models your living room.
- A place counts as “covered” at a deliberately low bar: 47 CFR 1.7004(c)(3)(i) sets it at a modeled 5 Mbps down / 1 Mbps up for 4G LTE and 7/1 Mbps for 5G-NR at the cell edge, at 90% cell edge probability and 50% cell loading. A green pixel is a prediction about that threshold, not about a good experience.
- We could not open the FCC National Broadband Map itself: broadbandmap.fcc.gov returned HTTP 403 to every request on September 13, 2026, as did every www.fcc.gov path. The federal sources above are therefore the rules and orders that govern the map, read on eCFR and docs.fcc.gov, not the map interface.
- Of the three nationwide carriers, only Verizon’s coverage page was readable from a server on September 13, 2026; t-mobile.com refused the whole origin and att.com returned a page with almost no extractable text. Verizon’s disclaimer is quoted as one carrier’s own words, not as evidence about the others.
- Congestion and prioritization are documented here at the level of plan and brand, not of your street. The FCC’s 2024 Communications Marketplace Report defines de-prioritization as “slowing data speeds during times of network congestion” and records that postpaid traffic often takes precedence over prepaid on the same network; it does not predict what happens at your address.
- ITU-R P.2109-2 is a standards-body recommendation, not U.S. government data, so we label it third-party under our own source tiers. It is a statistical model of building entry loss across a population of buildings — it explains why indoor results differ from an outdoor map, and cannot tell you the loss through your own walls.
- None of this makes a specific map wrong at a specific place. It establishes that the maps are predictions with published assumptions — which is why the only test that settles your address is a real device at your address.